Little is known of his early life. According to the Liber Pontificalis, he was a Roman, and his father's name was Priscus. Mark succeeded St. Sylvester as pope on the 18th of January, 336. He held office only eight months and twenty days, dying on the 7th of October following.[1]

Some evidence suggests that the early lists of bishops and martyrs known as the Depositio episcoporum and Depositio martyrum were begun during his pontificate. Per the Liber Pontificalis, Pope Mark issued a constitution investing the Bishop of Ostia with a pallium and confirming his power to consecrate newly elected popes. Also per the Liber Pontificalis, Pope Mark is credited with the foundation of the Basilica of San Marco in Rome, and a cemetery church over the Catacomb of Balbina, just outside the city on lands obtained as a donation from Emperor Constantine.[2]